| Specifications | . |
|---|---|
| Flash (program memory) | 4096b / 8192b ( 7552b with bootloader) |
| RAM | 256/512 bytes |
| EEPROM | 256/512 bytes |
| Bootloader | Yes, Optiboot w/Virtual Boot |
| GPIO Pins | 11 |
| ADC Channels | 12 (including the one on reset), many differential channels |
| PWM Channels | 6 |
| Interfaces | 2x UART, SPI, slave I2C |
| Clock options | Internal 1/8mhz, external crystal or clock up to 16mhz |
| Packages | SOIC-14, MLF-20 (QFN), VQFN-20 |
The ATtiny x41 series is a more advanced version of the ATtiny 84. It is pin compatible, though available only in surface mount packages, and offers an incredible array of peripherals, whilest costing only slightly more than an ATtiny 84. Tests have shown that despite manufacturer spec'ed max speed of 16mhz, they typically work without issue at 20mhz @ 5v and room temperature.
This core includes an Optiboot bootloader for the ATtiny841, operating on the hardware UART0 (Serial) port at 115200 baud for 12mhz or higher, or 57600 when running at lower speeds. The bootloader uses 640b of space, leaving 7552b available for user code. In order to work on the 841, which does not have hardware bootloader support (hence no BOOTRST functionality), "Virtual Boot" is used. This works around this limitation by rewriting the vector table of the sketch as it's uploaded - the reset vector gets pointed at the start of the bootloader, while the WDT vector gets pointed to the start of the application. As a consequence, the watchdog timer interrupt cannot be used if you're using the Optiboot bootloader (Watchdog reset still works). These issues are only relevant when programming through the bootloader. A version of the bootloader that operates on Serial1 is included in the bootloaders folder, though you will have to program it manually or modify boards.txt to use it.
Programming the ATTiny841 via ISP without the bootloader is fully supported.
The internal oscillator is factory calibrated to +/- 2%. +/- 2% is good enough for serial communication - however, this spec is only valid below 4v - above 4v, the oscillator runs significantly faster; enough so that serial communication does not work. This would interfere with uploads using the bootloader - to work around this, a version of Optiboot is included built assuming the slightly higher operating frequency; this will be used if you select the >4.0v operating voltage prior to doing Burn Bootloader. Although this fixes uploads, it is an awkward workaround (and won't work below 4v) - for this reason is recommended to use a crystal when using the serial ports above 3.3v.
There is no I2C master functionality implemented in hardware. As of version 1.1.3, the included Wire.h library will use a software implementation to provide I2C master functionality, and the hardware I2C slave for slave functionality, and can be used as a drop-in replacement for Wire.h with the caveat that clock speed cannot be set.
There is hardware SPI support. Use the normal SPI module.
There are two hardware serial ports, Serial and Serial1. It works the same as Serial on any normal Arduino - it is not a software implementation.
I (Spence Konde / Dr. Azzy) sell ATtiny841 boards through my Tindie store - your purchases support the continued development of this core.
The names of interrupt vectors used in the 841 and 441 are:
INT0_vect
PCINT0_vect
PCINT1_vect
WDT_vect (note: this is unavailable when using the bootloader, and the IDE will not warn you about it)
TIMER1_CAPT_vect
TIMER1_COMPA_vect
TIMER1_COMPB_vect
TIMER1_OVF_vect
TIMER0_COMPA_vect
TIMER0_COMPB_vect
TIMER0_OVF_vect
ANA_COMP0_vect
ADC_vect
EE_RDY_vect
ANA_COMP1_vect
TIMER2_CAPT_vect
TIMER2_COMPA_vect
TIMER2_COMPB_vect
TIMER2_OVF_vect
SPI_vect
USART0_START_vect
USART0_RX_vect
USART0_UDRE_vect
USART0_TX_vect
USART1_START_vect
USART1_RX_vect
USART1_UDRE_vect
USART1_TX_vect
TWI_SLAVE_vect